Hi everyone. I'm new to the Forum. I just purchased my first pair of vintage Kef's, but I've been a KEF fan for a good while with my main speakers being the more Modern XQ-40's which I love! I hooked up my recently acquired 105'2's yesterday, and MAN! These things deserve all of the praise they have received. They sound amazing! Having said that, I am experiencing one issue. I'm running them with a pair of Aragon palladium ii Mono blocks which are rated at 400 watts each. I realize that the 105'2's are rated at 200 watts max. The issue I'm having is that one of the speakers shuts off and on when i crank them up , and I'm assuming it's the S-Stop protection activating. The Red Peak indicator light is not coming on, and the other speaker plays fine. I am not clipping the amp, and the volume level although loud isn't Excessively loud and shouldn't be triggering the protection. Any suggestions on what I can do to eliminate this problem? I'm not a tech savvy kind of guy, but I do have some nearby friends that are. I'm thinking possibly bypass this protect circuit?? Thanks for any advice.

I've seen reviews where 1000W peak have been tolerated on wide dynamic range material for short periods of time so the speakers are by no means limited to 200W, there are too many variables in heating up the voice coils or driving beyond travel limits to be specific about music material wattage as opposed to constant sine waves.

I have Mk1s which had thermally matched fuses instead of the SStop and have used them for 30 years with the protection, but am not a heavy metal headbanger (or do high speed tape reeling anymore), but do play at realistic concert hall/opera house impact in a large room.

Not being familiar with the SStop internal circuitry (if anyone actually has any complete diagrams) I would guess one of your circuits has drifted. You could drive both in mono and see if the leds come on at the same time might give a clue.

Thanks for the reply. The LED's do not come on at all except when doing the initial setup. I just meant they are rated for 200 watts. I know generally clean power won't hurt speakers and these Aragons are top notch amps. I'm hoping someone may chime in with a suggestion. Maybe bypass the protect circuit or have the crossovers rebulit. I'be read something about a kit that can be ordered with new capacitors etc from Falcon Acousitcs. Anyone have any experiemce with that? if so, did it improve the sound? Thanks

I know it would be a lot of work, but you need to swap protection boards to see if the fault travels across. With one system working properly and the other cutting out prematurely, the best way to isolate the problem is by swapping parts across and back.

I did try turning the knob to the lower wattage setting last night, and the red lights never came on. As for swapping the protection boards, is that pretty easy to do once i get in there? I'm a dummy when it comes to that kind of stuff, but if its a simple unplug and swap out then of course i could do that.

I know it would be a lot of work, but you need to swap protection boards to see if the fault travels across. With one system working properly and the other cutting out prematurely, the best way to isolate the problem is by swapping parts across and back.

I do have some s-stop spares.

I have a very knowledgeable friend whom i plan to show the crossovers to once I pull them. Are the S-Stops something that can be "restored/repaired" or would replacements be in order from someone like you? thanks

I have a very knowledgeable friend whom i plan to show the crossovers to once I pull them. Are the S-Stops something that can be "restored/repaired" or would replacements be in order from someone like you? thanks

The passive power supply part of the s-stop board is made up of regular discrete wired components, four of which are electrolytic capacitors. These are the most likely components to have dried up and failed after all these years. The active psu high voltage transistors, rms detector, relay driver and other stuff is in four thick film modules. One is a resistor array. the other three were custom designed, only made for and supplied to KEF Electronics.

I have read that there are two versions of the 105.2's? I can't seem to find any info to know exactly how to tell. My serial number is 6154. I read it depends on your serial number?? Thanks again
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